A heater of this type is often used to hold a food carrier during serving or cleaning or while being eaten from or cooked on, and also positions the food carrier relative to the heat source and to a bearing surface, for example a table surface.
A heater of the mentioned type has become known through Swiss Patent No. 404 910. It consists substantially of a support frame for a food carrier and a heat source arranged a certain distance below the food carrier to assure optimum heat transmission.
Problems which occur when using the aforementioned heater arise in part because the heating means which are used, for example candles which are commonly called tea lights, cannot be adjusted or regulated in and of themselves with respect to the amount of heat produced, as can regulatable electrical heating plates. In addition, the flame intensity which exists when a candle is first lit and which is theoretically supposed to be continuous for a typical burning duration of approximately 30 to 40 minutes is in practice influenced by two factors. First, the amount of the wax feeding the flame is reduced with time, and second, the condition of the wick changes. The latter can be due to a natural burning off or, as is important to the invention, to breaking or bending of the wick during handling of the candle between uses.
In order to assure after repeated use a flame with sufficient heat, appropriate initial conditions with respect to the wick could be chosen during design, but this leads to a very strong initial flame intensity.
In the case of the usual serving heaters having relatively large serving plates on which foods are kept warm during the first and second offerings, a heat action which is initially too strong is of no great importance, since the good capability for heat conduction in the serving plates, which typically consist of metal, assures a broad surface distribution.
Compared with this, a flame intensity which is initially too high in so-called plate service heaters is unfavorable in many respects. Here, eating takes place directly from poor heat-conducting ceramic or glass plates, whereby only a small zone in the center of the plate which is approximately 10 cm in diameter is heated. If this zone becomes too hot, due to the flame action, there is a danger that the foods thereon will be overheated or burned or that the plate itself will break. Furthermore, there is the possibility that a fork which rests for a short time in the center of the plate will be heated up sufficiently to cause uncomfortable burning of the lips. Moreover, with respect to the desire to eat food warm, there are different individual opinions concerning the degree of heat which is appropriate.
To resolve all of this, it has already been suggested that the heat source can be arranged so that its distance from the bottom of the plate can be varied. However, this requires the provision of extra vertical space for effecting the adjustment, and thus results in an increased vertical height for the heater and food plate thereon, as a result of which the user must relinquish a normal eating position.
A further known suggestion is to arrange an apertured sheet-metal plate between the candle flame and the bottom of the food plate, the apertured plate preventing the flame from acting directly onto the food carrier. This device prevents localized overheating during use of regulatable heat sources, but during use with candles, which is common up to 90% of the time, the disadvantage had to be accepted that, for example in the case of candles which had been used already several times, changes in the flame action can occur due to the burning off of the wick and the heat which is then produced is sometimes insufficient to pass the apertured plate. To compensate for this, and as a type of make-do solution, one can remove the apertured plate while eating, but only by first removing the food plate from the heater, which is a disadvantage.
Independent of the handling difficulties associated therewith, the use of apertured sheet-metal plates has also resulted in two further problems. First, if after use the food plates are removed from the frames but the candles are not removed, the candle wicks are subjected to the danger of breaking off during space-saving vertical stacking of the heaters and thus become unusable, possibly after only one use. However, if the apertured plates are not removed, then the frames cannot be efficiently stacked in and above one another.
To eliminate these described disadvantages, a control mechanism is needed which permits a user to carry out with a minimum apparatus height an adjustment of the amount of heat applied from the heat source to the food carrier according to individual desires without having to remove the food carrier during eating and, moreover, permits vertical stacking of the heaters in an efficient manner.
Difficulties which stand in the way of this objective include, for the main purpose of use of the heaters, to serve as very flat vertically low heat-providing means during eating or cooking at the table, minimal space remains between the flame and plate bottom. In addition, the releasable interconnection between the food carrier and heater frame, which is necessary for secure handling of the combined frame and food carrier, does not permit utilization of a control mechanism in which the plate, for example a heated metal plate, must be removed from the frame or which, due to its structure, requires a large amount of space.
Moreover, the use of the heater, for example in a busy restaurant, must be easy to handle during clearing of tables. The individual heaters, after removal of the plates and in spite of the heat-controlling mechanism and inserted candles, are to be space-savingly stackable on one another and preferably into one another, so that they stay together as a whole and can be used again.